Flooding of forested valleys by reason of natural causes or by reason of hydroelectric damming has left submerged forest as unharvested free standing trees. A substantial percentage of the submerged free standing trees are within depths of approximately 100 feet of water and so are available to be harvested given an appropriate log cutting and retrieval mechanism.
As opposed to well understood dry land logging practices, the harvesting of submerged free standing trees presents many obstacles. Such obstacles include the fact that if manual divers are used to dive to the base of such trees, to either cut through the tree trunks using saws or other means such as blasting to uproot or free the tree, the diver is faced with severe restrictions on the amount of time that may be spent at such depths. Further, the difficulty of wielding saws or the like in an underwater environment can prove dangerous to the diver. Because a majority of the submerged free standing trees are waterlogged, they will not rise to the surface of their own accord once uprooted or otherwise freed from the bottom and so must be retrieved by means of cables, flotation bags or the like. The result is a slow process which does not yield many logs harvested in a typical day. In the case of some of the larger submerged free standing trees, they are so large, because they form part of very old stands of timber, that unassisted manual sawing is very difficult and retrieval slow and difficult.
A further obstacle relates to underwater visibility. It is known in the prior art to attempt underwater cutting or sawing of submerged elongate objects such as logs or pilings, but what is not addressed is the fact that activity at or near the mudline results in stirring up of silt or the like which quickly makes seeing underwater difficult if not impossible. Such difficulties are in addition to the normal darkness one would anticipate at depth. However, the solution to the problem is not merely the use of underwater lighting. By way of analogy, the problem is akin to the use of driving headlights when set on high beam in a snowstorm. The result is merely a whiteout. Thus, because it is desired to saw or cut submerged free standing trees near their base so as to maximize the recovery of the timber, a means must be provided for clearing, or seeing through, the murky water if is it desired to use a remotely actuated mechanical device employing a real time imaging system for positioning the gripping and sawing or cutting means.
In the prior art, applicant is aware of U.S. Pat. No. 3,667,515 which issued Jun. 6, 1972 to Corey for a Pile Cutting Device. Corey teaches a pile cutting device for use in locations remote from the operator. A pile cutter suspended on a cable is lowered by means of a crane to a desired depth, for example, to the bottom of a water body. The base of the pile cutting device is lowered so as to journal the pile in the base as base is lowered. The base has a guide across which is swept a selectively actual blade. The blade shears the pile at its base.
Applicant is also aware of U.S. Pat. No. 3,693,676 which issued on Sep. 26, 1972 to Burch for an Underwater Pile Cutting Saw. Burch discloses a power saw capable of being manually manipulated above the surface of a body of water for cutting off pilings and the like adjacent to the bottom. A locator member engages around the piling or object to the cut and includes a post about which a saw swings, so as to swing across the locater member to cut off the piling or object. The locator member and saw may be manipulated from a boat, barge, dock or the like, it being an object of the Burch device to eliminate pilings and other objects adjacent the bottom as navigational hazards.
Applicant is further aware of U.S. Pat. No. 4,168,729 which issued Sep. 25, 1979 to Tausig et at for an Underwater Self-gripping Pile Cutting Device. As in the Corey device, Tausig et al teach a shearing pile cutter lowerable by means of a cable onto a pile. The shear cutter assembly has self-gripping teeth or spikes incorporated as part of the cutting blades to hold the pile and prevent slipping during cutting operations. As the hydraulically operated scissor-type cutter blades close about the pile, the spikes bite into the timber and keep the blades from squeezing off the pile.